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Lecture 11

NUTR 3210 Lecture 11: micronutrients part 2

6 Pages
84 Views
Spring 2018

Department
Nutrition
Course Code
NUTR 3210
Professor
David Mutch
Lecture
11

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Micronutrients part 2 micronutrients involved in oxidant defense
Reduction-Oxidation Reactions
Reduction-oxidation reaction aka redox reaction
- Involves the transfer of electrons between two
substrates
- Many biochemical reactions are essentially electron
transfers
Large number of micronutrients have redox functions
The primary electron carriers in the body are NADH and
FADH2
This is important for the creation of ATP
Reactive Oxygen Species (ROS)
ROS produced as a by-product of the ETC when
proper electron flow fails ~% leakage
Occurs in O2 rich environment where oxygen can
react with electrons
Radicals have unpaired electrons
- /unpaired electron means imbalanced
electrons
- / want to get rid of imbalance so will get rid of
electrons
- /radicals are produced in any cell that has a
mitochondria
Mutations in SOD = Lou Gehrigs
- ROS are linked to disease
H2O2 converted to H2O by catalase, glutathione
peroxidase (selenium dependent enzymes)
(owever, ROS arent always bad remember T
and T4 production)
/1% of electrons from the mitochondria leak out and react with O2 which
leads to ROS
/SOD formed by oxygen and electron which is a radical (?)
- SOD takes another electron from copper or zinc and will from H2O2
/if H2O2 interacts with leaked out electron, it will become a hydroxyl
radical which is hugely reactive
- Hydroxyl radical will go attack DNA, lipids which can lead to cancer
and so forth
Vitamin E
Encompasses 8 compounds (vitamers)
- 4 tocopherols
o Have saturated side chains with 16 carbons
- 4 tocotrienols
o Have unsaturated side chains with 16 carbons
Vitamers in both classes , , , 
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Only -tocopherol has significant activity in the body
No inter-conversion of vitamers in animals
All are found naturally in foods
Tocopherol derived from greek word:
- Tokos = child birth & phero = to bear or bring forth
- Based on work showing that rats couldnt reproduce when vitamin E was absent from the diet
Vitamin E 4 tocopherols
Saturated side chain (phytyl tail)
Nomenclature used to describe # and position of ring CH3 groups
= most methylated ring
***the hydroxyl group is the antioxidant side
Found free in foods
- Found in almonds, dietary plant oils, etc.
- Absorbed passively
R and S refers to chiral carbon configuration of methyl groups on side chain
Natural -tocopherol is RRR
- Fits in tocopherol transfer protein (TTP)
- /most important is normal -tocopherol RRR since it can fit in to TTP
- /TTP will move -tocopherol around the body
/differences important in bioactivity in the body since methyl groups are in different spots
Vitamin E 4 tocotrienols
Unsaturated side chain (phytyl tail)
Nomenclature rules the same as tocopherols
Found esterified in foods
- Legumes, grains, etc.
- Pancreatic esterase required for absorption
Lower levels in food compared to tocopherols
Tocotrienols have anti-oxidant activity in the liver only not converted to -tocopherol or recognized by TTP)
Vitamin E intake
Food source -> nuts, seeds, vegetable oils, leafy greens
- Sensitive to food preparation & storage (e.g. roasting nuts decrease vit E levels)
- Mostly obtained from plants because stored in fat in animals and we dont typically eat the fat
RDA established using only -tocopherol
- Estimated based on crude tests examining RBC hemolysis (releases haemoglobin) in the presence of dilute
H2O2
- (>20% RBC hemolysis means there is a Vit E deficiency)
RDAs for Vit E can be reported as either mg or )U
UL = 1,000 mg/day (causes increased bleeding)
- But gastrointestinal problems could be seen at lower levels than the UL
Deficiency? Very rare, but can occur in:
- Premature infants
- People with fat malabsorption disorders or gallbladders removed
- People with genetic defects in lipoproteins or TTP
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Description
Micronutrients part 2 micronutrients involvedinoxidantdefense Reduction-Oxidation Reactions Reduction-oxidationreaction aka redox reaction - Involvesthe transfer ofelectrons between two substrates - Many biochemical reactions are essentiallyelectron transfers Large number ofmicronutrients have redox functions The primaryelectron carriersin the body areNADHand FADH2 Thisisimportant for thecreation of ATP Reactive Oxygen Species (ROS) ROSproduced asa by-product of the ETC when proper electron flow fails(~1%leakage) Occursin O2 rich environment where oxygen can react with electrons Radicalshave unpaired electrons - /unpaired electron meansimbalanced electrons - /want toget rid of imbalance sowillget ridof electrons - /radicalsare produced inany cellthat hasa mitochondria Mutations in SOD =Lou Gehrigs - ROSare linked todisease H2O2 converted toH2Oby catalase, glutathione peroxidase (seleniumdependent enzymes) However,ROSarent alwaysbad (remember T3 and T4 production) /1%of electrons from the mitochondria leak outand react withO2which leadstoROS /SODformed by oxygenand electron which isaradical(?) - SODtakesanother electron from copper or zincand willfromH2O2 /ifH2O2 interactswith leaked out electron,it will becomeahydroxyl radical which ishugely reactive - Hydroxylradical will goattack DNA,lipidswhichcan lead tocancer and soforth Vitamin E Encompasses 8compounds(vitamers) - 4 tocopherols o Have saturated side chains with 16carbons - 4 tocotrienols o Have unsaturated sidechains with16carbons Vitamers in both classes (, , , ) Only -tocopherol has significant activity inthebody Nointer-conversion of vitamersin animals Allare found naturally infoods Tocopherol derivedfromgreek word: - Tokos=child birth & phero=tobear orbringforth - Based on work showing that rats couldnt reproducewhen vitaminEwasabsent fromthe diet Vitamin E 4 tocopherols Saturated side chain (phytyl tail) Nomenclature usedto describe #and positionofringCH3groups =most methylated ring ***the hydroxyl group isthe antioxidant side Found free in foods - Found in almonds,dietary plant oils,etc. - Absorbed passively Rand S referstochiralcarbon configurationofmethylgroupsonsidechain Natural -tocopherol isRRR - Fitsin tocopherol transfer protein (TTP) - /most important isnormal -tocopherolRRR sinceit can fit intoTTP - /TTP willmove -tocopherol aroundthe body /differencesimportant inbioactivity in the bodysince methylgroupsareindifferent spots Vitamin E 4 tocotrienols Unsaturated side chain (phytyl tail) Nomenclature rules the same astocopher
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